Originally Posted by
cblaisd
Mountain-wave/rotor turbulence is a third kind of turbulence that can make for controllability issues particularly in light aircraft. Very intense "spinning" vortices can develop over mountain ranges and no aircraft wants to get caught in one of those, particularly light aircraft.
As did this BOAC 707 near Mt. Fuji in 1966
http://www.pilotfriend.com/disasters/crash/boac911.htm